Low budget CV/Gate sequencer

Similar projects worth following
A cheap yet versatile step sequencer built around the CD4017 decade counter IC.

The goal of this project is build a simple step sequencer with two rows of eight steps. Planned features: CV/Gate outputs, internal or external clock control; clock divider; start/stop; variable sequence length.

The ticking heart of this project is a 555 timer that clocks a 4017 decade counter thru a maximum of eight steps. A 4024 IC will be used to divide the clock frequency by factor 2, 4, 8, 16, 32 and 64. This can be used to clock row B (CD4017 number 2).

  • 2 × CD4017 decade conter IC
  • 1 × 74HC32 Quad OR Gate IC
  • 2 × 100K Ohm resistor
  • 16 × blue LED
  • 2 × 330 Ohm resistor current limiters for the LEDs

View all 8 components

  • First Row

    Mark06/25/2016 at 15:52 0 comments

    The outputs from both decade counters will be routed to two rows of eight output channels. Each channel features a potmeter for CV adjustment and a step indicator LED. Individual gate outputs will be added at a later stage.

    Major rethink! After several trials, I've decided to mount the potmeters and LEDs directly on a panel and not on PCB's. They got too crowded and it would have been almost impossible to repair. Instead I will use bits of stripboard as wiring posts. Simple does it.

  • The Brain

    Mark06/19/2016 at 16:17 0 comments

    I've got lots of small prototype PCB's so it makes sense to break this project up into several modules. This is my first attempt at designing the central unit aka brain of the sequencer. This module contains all the IC's and will connect to the output module(s) with jackports and LEDs. I've already built a simple LFO module that will provide the clock signal. This will be a stripped-down version with minimal functionality for test and demonstration purposes.

    Second row wiring diagram:

    I've started building the circuit. I've soldered the chip sockets into place and about 80% of the wiring is done. I'm waiting for the 100K resistors to arrive in the mail before I will proceed with the rest of the work.

    UPDATE: I've updated the wiring diagrams for clarity. Haven't been able to source a suitable 4 position switch to select the clock signal for the second row so I have just added 4 female DuPont headers and soldered a male cable to the clock input of the second decade counter.

    The brain is ready! I've soldered all the wires and it's messy spaghetti. Lesson learned: don't go with the very first layout you can think of; make one or two revisions before you start the build.

    A bit too complicated for comfort! Wiring this was quite a challenge. And it won't be easy to fix or repair if something goes wrong. So I decided to start off by building a simpler brain module that will control only one row of steps. The clock divider and second row will be moved to separate boards. And i'll probably use a pair of dual J-K flip-flop ICs for the clock frequency divider.

    I present the Mini Brain, revision C:

View all 2 project logs

Enjoy this project?



Mark wrote 07/01/2016 at 14:13 point

Thank you for your kind comments! You're right; it's my intention to end up with a low budget modular synth.

To be honest, I'm a noob in electronics and in soldering and I'm very much "learning on the job". So I'm still figuring out the proper or smart way to do things. I have used solder bridges in places, usually when there's only a short distance to ehh... bridge.

The original brain design was just wrong - too much stuff, not enough space, awkward layout. But balancing my ambitions with my actual skills is part of the learning process :)

  Are you sure? yes | no

0xF wrote 07/01/2016 at 15:04 point

Neat project, I recall years ago having the ambition (but lacking literally everything else) to make such a thing; I might follow your designs one day though :) I too am fairly noobish, I feel I'm in the "know enough to make a mess" state of things, but I did found that solder bridging is at least easier to follow and compare to drawings, and with a couple afternoons of practice it's doable.

Good luck

  Are you sure? yes | no

0xF wrote 06/30/2016 at 23:48 point

Hi!Cool job with all the audio circuits, you look like you'll have a whole synth running soon!

Have you thought about using solder bridges instead of all wires?It's reasonably easy to modify and makes it looks less messy; it also is a design less prone to accidentaly tearing off wires IHMO.


  Are you sure? yes | no

Similar Projects

Does this project spark your interest?

Become a member to follow this project and never miss any updates